Commitments and Contingencies - Narrative (Details) $ in Millions	1 Months Ended	9 Months Ended
	Nov. 30, 2020 USD ($)	Sep. 30, 2023 USD ($) mGPSite	Dec. 31, 2022 USD ($)
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross		$ 434.0	$ 409.0
Accrual For MGP Investigation And Remediation [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross		$ 345.0	355.0
Commonwealth Edison Co
Commitments And Contingencies Additional Narrative Information [Line Items]
Mgp Site Contingency Monitoring Count | mGPSite		19
Deferred Prosecution Agreement Payments	$ 200.0
Loss Contingency Accrual		$ 46.2
Customer Refund Liability, Current		38.0
Accrual for Environmental Loss Contingencies, Gross		312.0	325.0
Commonwealth Edison Co | Accrual For MGP Investigation And Remediation [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Period Increase (Decrease)		25.0
Accrual for Environmental Loss Contingencies, Gross		311.0	324.0
Commonwealth Edison Co | Illinois Chamber of Commerce
Commitments And Contingencies Additional Narrative Information [Line Items]
Customer Refund Liability, Current		$ 31.0
PECO Energy Co
Commitments And Contingencies Additional Narrative Information [Line Items]
Mgp Site Contingency Monitoring Count | mGPSite		6
Accrual for Environmental Loss Contingencies, Gross		$ 28.0	25.0
PECO Energy Co | Accrual For MGP Investigation And Remediation [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross		$ 26.0	23.0
Baltimore Gas and Electric Company
Commitments And Contingencies Additional Narrative Information [Line Items]
Mgp Site Contingency Monitoring Count | mGPSite		4
Accrual for Environmental Loss Contingencies, Gross		$ 9.0	9.0
Baltimore Gas and Electric Company | Accrual For MGP Investigation And Remediation [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross		8.0	8.0
Pepco Holdings LLC
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross		82.0	46.0
Pepco Holdings LLC | Accrual For MGP Investigation And Remediation [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross		0.0	0.0
Potomac Electric Power Company
Commitments And Contingencies Additional Narrative Information [Line Items]
Environmental Liability - Anacostia		47.0
Environmental Liability - Buzzard Point		10.0
Accrual for Environmental Loss Contingencies, Gross		80.0	44.0
Potomac Electric Power Company | Accrual For MGP Investigation And Remediation [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross		$ 0.0	0.0
Delmarva Power and Light Company
Commitments And Contingencies Additional Narrative Information [Line Items]
Mgp Site Contingency Monitoring Count | mGPSite		1
Accrual for Environmental Loss Contingencies, Gross		$ 1.0	1.0
Delmarva Power and Light Company | Accrual For MGP Investigation And Remediation [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross		0.0	$ 0.0
Exelon Business Services Co Affiliate
Commitments And Contingencies Additional Narrative Information [Line Items]
Deferred Prosecution Agreement Liability, Current		173.0
Insurers' Settlement Payment		40.0
Settling Shareholders' Attorney Fees		$ 10.0